with questionable stock hydo's

and a mild hydro-cam, you should be OK with a __new _set of stock type (no chinee) lifters,for this man. When they are all adj. properly and you fire it up it may take 10-20 seconds before the oil system press. up and quietens down. While you have the lifter-blocks off be sure you are getting oil up to the lifter blocks and through them OK. When working prop. they should be very quiet.